Mosfet destructive testing.

[Arlo1]

Hi Guys,
I'm working some numbers and trying to see some real world FET current limits with the mounting/cooling and possible current flowing techniques I plan to use.
I need to gather data to find weather its worth running the big expensive fets or more smaller fets in parallel. I am aiming for high power as usual so I need to collect all data I can before moving forward and picking how many of what I will parallel with what design I decide to use.
I will find better ways to do more testing incl. a switching on and off test. All in time.
[youtube]GlzOFCTPk0A[/youtube]

 

[jonescg]

Hey Arlin, can you add a circuit diagram to explain how you're testing these? I think I know how you've done it, but a schematic would help a lot.

 

[Arlo1]

Hey Arlin, can you add a circuit diagram to explain how you're testing these? I think I know how you've done it, but a schematic would help a lot.

I am turning the fet on and keeping it on the whole time with 15v applied to the gate from the power supply.

Then simply hocking the source leg to the negative of the battery and the drain to one side of the load tester and the other side of the load tester to the positive of the batteries.
I'm just trying to see how much current you can flow though the mosfet it self. NO circuit required.

 

[jonescg]

So something like this?



What would varying the gate voltage do? Limit the current flow linearly?

 

[Arlo1]

So something like this?



What would varying the gate voltage do? Limit the current flow linearly?

To turn a mosfet on you put voltage to the gate in reference to the source. So source is - gate is + I used 15v to the gate. You do not want to turn the gate on only part way the mosfet will become a multi thousand watt heater the second its only partially conducting. Think of a bad connection with hi amps flowing thought it and how hot it gets
The 66v DC lipo pack is not always 66v I varied the voltage to control current.

 

[John in CR]

.

 

[liveforphysics]

That looks like so much fun Arlo!

Great video! The little guys are pretty tough! It would be interesting to add one of the new Ti nextFet 100v parts in to see how it fairs vs the 4110.

 

[jonescg]

So something like this?



What would varying the gate voltage do? Limit the current flow linearly?

To turn a mosfet on you put voltage to the gate in reference to the source. So source is - gate is + I used 15v to the gate. You do not want to turn the gate on only part way the mosfet will become a multi thousand watt heater the second its only partially conducting. Think of a bad connection with hi amps flowing thought it and how hot it gets
The 66v DC lipo pack is not always 66v I varied the voltage to control current.

Gotcha. So reverse the polarity of the LiPo pack in my drawing and we're pretty close.

It's just that electrical components with more than two legs confuse me :lol:

 

[Arlo1]

That looks like so much fun Arlo!

Great video! The little guys are pretty tough! It would be interesting to add one of the new Ti nextFet 100v parts in to see how it fairs vs the 4110.

Thanks it was fun the heart gets going and you can get a pretty big plasma ball
I'm interested in testing anything with potential people can send anything they think is worth it and I will find some better test equipment as well.
Next I think I'm going to test how long the ixfk230n20t and the irfp4568 last at 147 amps till they blow.

 

[liveforphysics]

Those pictures are badass.

 

[gwhy!1]

So something like this?

View attachment 1

What would varying the gate voltage do? Limit the current flow linearly?

Also in your diagram you don't have the load ... if you wired this up as it is shown you will damage your battery..

edit:

something like this:

 

[Arlo1]

Thanks gwhy. I didn't think that really mattered because I'm just trying to measure the current vs heat vs limits in a single MOSFET.
As drbass points out I will make sure my flir is reading the aluminum temp correctly. Then I will play with cooling technology and different compounds between the fet and aluminum or what ever I use for a heat sink.